1. Field of the Invention
The present invention relates to a metal belt for a continuously variable transmission, the metal belt being wound around a drive pulley and a driven pulley so as to transmit driving force, in which the metal belt includes a plurality of metal elements which are supported by a metal ring assembly, and in order to adjust gaps between the metal elements, a plurality of adjuster metal element groups are disposed on the metal belt at predetermined intervals, each of the adjuster metal element groups including at least two or more continuous adjuster metal elements whose thickness differs from that of the metal elements.
2. Description of the Related Art
Japanese Utility Model Publication No. 2-37307 has made publicly known a metal belt for a continuously variable transmission in which multiple metal elements (blocks) are supported by metal ring assemblies (hoops), and gaps between adjacent metal elements are adjusted by incorporating a predetermined number of adjuster metal elements, whose thickness differs from that of the metal elements, into the metal belt.
A problem with this metal belt for a continuously variable transmission is that if a width of the adjuster metal elements in a pulley axial direction is wider than a width of the metal elements in the pulley axial direction because of their variations which occur during manufacturing, the adjuster metal elements are pushed outward of the metal elements in a pulley radial direction; and large bending stress needs to be prevented from acting on part of the metal ring assemblies where the adjuster metal elements are pushed outward of the metal elements in the pulley radial direction. In order to solve the problem, the part of the metal ring assemblies acted on by the bending stress (in other words, the part of the metal ring assemblies where the adjuster metal elements are incorporated into the metal belt) is decreases in size by continuously disposing at least two or more adjuster metal elements on the metal belt. In addition, durability of the metal belt is enhanced by reducing a deformation amount of the part of the metal ring assemblies where the adjuster metal elements are incorporated into the metal belt.
Meanwhile, the metal elements and the adjuster metal elements, which differ from each other in thickness, not only differ from each other in weight, but also slightly differ from each other in shape, other than in thickness, because the metal elements and the adjuster metal elements are press-formed using different dies. It is inevitable that weight balance and shape balance slightly differ between a part of the metal belt corresponding to an adjuster metal element group where multiple adjuster metal elements are continuously disposed and the rest of the metal belt. As a result, a driving-side chord portion of the metal belt, which is situated between a drive pulley and a driven pulley, vibrates due to exciting force acting on the part of the metal belt corresponding to the adjuster metal element group so that noises and deterioration in power transmission efficiency may be caused.
A conceivable measure to avoid this is such that: the adjuster metal element group is divided into multiple adjuster metal element groups; the multiple adjuster metal element groups are disposed on the metal belt at predetermined intervals; and thereby, imbalance is reduced between the adjuster metal element groups. However, in this measure, intervals between the adjuster metal element groups become smaller so that a situation occurs in which some adjuster metal element groups exist on the driving-side chord portion at the same time, and a vibration condition of the metal belt may be compounded by exciting force applied to the multiple adjuster metal element groups against the intention to reduce the vibration of the metal belt.